Hillmann et al have described holoscopy, which is similar to digital holography, where a full field Fourier Domain optical coherence tomography (FD-OCT) image is recorded by exposing a 2D sensor array to the light scattered from an object and reference surface from a swept frequency source (D. Hillmann et al, “Holoscopy—holographic optical coherence tomography” Optics Letters 36(13): 2390 2011 hereby incorporated by reference). In holoscopy, unlike classic OCT, the sensor array is typically imaged to the far field of the object rather than to the object. As a result, each sensor element on the 2D array records light scattered in a different direction, encoding a lateral spatial frequency, rather than light from a different position on the object. The axial spatial frequencies are encoded by the optical frequency of the source, just like in swept-source OCT. The data may be reconstructed to a volume by three-dimensional Fourier transform. The reconstruction is notable in that high lateral resolution and power efficiency can be achieved far from the equivalent Rayleigh range calculated from the numerical aperture of the system. Full field systems may also allow a greater amount of light (Maximum Permissible Exposure) than point scanning systems on sensitive tissues such as the eye as the illumination is not focused to a point on the retina. By detecting at a defocused plane, the reconstruction combines information from a larger number of sensor elements to a single output pixel. This method requires a very fast camera and a high power swept source. Full field systems are also particularly susceptible to multiply scattered photons, and light scattered or reflected from surfaces far from the object of interest because they have no confocal light restriction.
Nakamura et al described a line-field spectral domain OCT system that could acquire spectral domain data for a full B-scan in a single exposure of a 2D array (Y. Nakamura, et al, “High-speed three dimensional human retinal imaging by line-field spectral domain optical coherence tomography” Optics Express 15(12):7103 2007 hereby incorporated by reference). A vertical line of light was imaged onto the retina of an eye and reimaged onto the entrance silt of a spectrometer. Each point at the entrance slit of the spectrometer corresponded to a portion of the retina object under observation. The spectrometer decomposed the light from each point on the entrance slit of the spectrometer into a spectrum represented as a column on the 2D sensor. A standard SLD and common 2D image sensor could be used; effectively achieving a motion artifact free B-scan without very high speed electronics Like full field systems, the laterally distributed light allows a much greater exposure on sensitive tissues. Unlike the full field holoscopy systems described earlier, the sensor array in this design is imaged to the retina, rather than to the far field of the retina. The simple one-dimensional data reconstruction along the axial direction suggests that the system has the same limits of lateral resolution typically experienced by flying-spot OCT systems. The confocal gate in one lateral dimension, created by the narrow line illumination and the spectrometer entrance slit, is partially effective at eliminating light scattered from out of focus planes. Because of system aberrations, likely in the spectrometer, the system suffered from a strong SNR roll-off at the edges of the line profile.